Predominantly Cytoplasmic Localization in Yeast of ASR1, a Non-Receptor Transcription Factor from Plants



Nicolás Urtasun1, Susana Correa García1, Norberto D Iusem2, Mariana Bermúdez Moretti*, 1
1 Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Ciudad Universitaria (1428), Buenos Aires, Argentina
2 Laboratorio de Fisiología y Biología Molecular, Departamento de Fisiología, Biología Molecular y Celular and IFIBYNE-CONICET, Facultad de Ciencias Exactas y Naturales, Ciudad Universitaria (1428) Buenos Aires, Argentina


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© Urtasun et al.; Licensee Bentham Open.

open-access license: This is an open access article licensed under the terms of the Creative Commons Attribution Non-Commercial License (http: //creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided the work is properly cited.

* Address correspondence to this author at the Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Ciudad Universitaria (1428), Buenos Aires, Argentina; Tel: 005411 4576 3300; Fax: 005411 4576 3342; E-mail: mariana@qb.fcen.uba.ar


Abstract

The Asr gene family (named after abscisic acid, stress and ripening), currently classified as a novel group of the LEA superfamily, is exclusively present in the genomes of seed plants, except for the Brassicaceae family. It is associated with water-deficit stress and is involved in adaptation to dry climates. Motivated by separate reports depicting ASR proteins as either transcription factors or chaperones, we decided to determine the intracellular localization of ASR proteins. For that purpose, we employed an in vivo eukaryotic expression system, the heterologous model Saccharomyces cerevisiae, including wild type strains as well as mutants in which the variant ASR1 previously proved to be functionally protective against osmotic stress. Our methodology involved immunofluorescence-based confocal microscopy, without artificially altering the native structure of the protein under study. Results show that, in both normal and osmotic stress conditions, recombinant ASR1 turned out to localize mainly to the cytoplasm, irrespective of the genotype used, revealing a scattered distribution in the form of dots or granules. The results are discussed in terms of a plausible dual (cytoplasmic and nuclear) role of ASR proteins.

Keywords: ASR proteins, water stress, intracellular localization, Saccharomyces cerevisiae, confocal microscopy.